Implantable defibrillator system with capacitor switching circuitry

Abstract

The present invention uses switches to set the topology and polarity of a circuit that includes capacitors to deliver an electric pulse to a heart during a defibrillation procedure. The waveform of the electric pulse is biphasic, in that it is a positive portion of the pulse followed by a negative portion of the pulse. The topology and polarity of the circuit are utilized to produce a waveform that approximates the ideal waveform for the specific situation. The circuit provides for combinations of capacitors variously in series and in parallel and changing the topology and polarity of the circuit during discharge of the capacitors.

We claim: 
     
       1. An improved implantable defibrillator system for producing a capacitive-discharge electrical countershock, the implantable defibrillator system being a self-contained human implantable device including a capacitor means for storing an electrical charge, means for internally charging the capacitor means, means for sensing a cardiac dysrhythmia in a human patient and means for selectively discharging the electrical charge as an electrical countershock to be delivered through at least two implantable discharge electrodes in response to the means for sensing the cardiac dysrhythmia, the improvement comprising: the capacitor means including at least two separate capacitor units, each capacitor unit having a separately electrically accessible anode output and a separately electrically accessible cathode output; and   the means for selectively discharging the electrical charge including electronic switching circuitry means electrically connected between at least one output of each capacitor unit and electrically connected between at least one output of each capacitor unit and each of the at least two implantable discharge electrodes for selectively electrically connecting the anode output and the cathode output of the at least two capacitor units to the at least two implantable discharge electrodes to independently establish both a topology and a polarity for the electrical countershock during a discharge period of time when the electrical charge is discharged such that the topology is selectable from the group consisting of a parallel configuration of the capacitor units, a series configuration of the capacitor units, a sequential configuration of the capacitor units, or any combination thereof.   
     
     
       2. The implantable defibrillator system of claim 1 in which the electronic switching circuitry means selectively changes the polarity of the electrical countershock once to produce an initial portion and a succeeding portion of a biphasic waveform. 
     
     
       3. The implantable defibrillator system of claim 2 in which the electronic switching circuitry means changes the topology during the initial portion of the biphasic waveform. 
     
     
       4. The implantable defibrillator system of claim 2 in which the electronic switching circuitry means changes the topology during the succeeding portion of the biphasic waveform. 
     
     
       5. The implantable defibrillator system of claim 1 in which the electronic switching circuitry means selectively discharges in sequence at least a portion of the electrical charge stored by the at least two capacitor units. 
     
     
       6. The implantable defibrillator system of claim 5 in which the electronic switching circuitry means selectively changes the topology after the portion of the electrical charge is discharged in sequence and then selectively discharges at least a second portion of the electrical charge stored by at least one of the at least two capacitor units. 
     
     
       7. The implantable defibrillator system of claim 1 in which there are two capacitor units, each of which is comprised of a pair of electrolytic capacitors electrically connected in series.